93-95% Purity Alumina (ASTM D2442 Type II, IEC 60672 Type C-786)
Type II alumina is a grade of alumina. It has the lowest strength compared to the other variants of alumina. The graph bars on the material properties cards below compare type II alumina to other oxide-based engineering ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Compressive (Crushing) Strength
2260 MPa 330 x 103 psi
Elastic (Young's, Tensile) Modulus
270 GPa 40 x 106 psi
Flexural Strength
320 MPa 46 x 103 psi
Fracture Toughness
3.9 MPa-m1/2 3.6 x 103 psi-in1/2
Knoop Hardness
1120
Poisson's Ratio
0.22
Shear Modulus
120 GPa 18 x 106 psi
Tensile Strength: Ultimate (UTS)
210 MPa 30 x 103 psi
Electrical Properties
Dielectric Constant (Relative Permittivity) At 1 Hz
9.0
Dielectric Constant (Relative Permittivity) At 1 MHz
8.7
Dielectric Strength (Breakdown Potential)
12 kV/mm 0.48 V/mil
Electrical Dissipation At 1 Hz
0.00067
Electrical Dissipation At 1 MHz
0.00073
Electrical Resistivity Order of Magnitude
13 10x Ω-m
Other Material Properties
Density
3.7 g/cm3 230 lb/ft3
Maximum Temperature: Mechanical
1550 °C 2820 °F
Maximum Thermal Shock
250 °C 480 °F
Melting Onset (Solidus)
2040 °C 3700 °F
Specific Heat Capacity
900 J/kg-K 0.22 BTU/lb-°F
Thermal Conductivity
19 W/m-K 11 BTU/h-ft-°F
Thermal Expansion
7.2 µm/m-K
Common Calculations
Stiffness to Weight: Axial
41 points
Stiffness to Weight: Bending
59 points
Strength to Weight: Axial
16 points
Strength to Weight: Bending
21 points
Thermal Diffusivity
5.8 mm2/s
Thermal Shock Resistance
7.7 points
Followup Questions
Further Reading
ASTM D2442: Standard Specification for Alumina Ceramics for Electrical and Electronic Applications
Ceramic and Glass Materials: Structure, Properties and Processing, James F. Shackelford and Robert H. Doremus (editors), 2008
Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012
IEC 60672-3: Ceramic and glass-insulating materials - Part 3: Specifications for individual materials
Springer Handbook of Condensed Matter and Materials Data, W. Martienssen and H. Warlimont (editors), 2005